Question

What is probability of randomly selecting a marble and getting black or red? a bag contains 5 black marbles, 10 red marbles, and 20 blue marbles?

Answer 1

This is a mutually exclusive event because you can't choose both at the same turn you can only pick one or the other. so we add the event chances together,
5/35 + 10/35 = 15/35 or reduced 3/7